ARM: wire up getrandom syscall

Add the new getrandom syscall for ARM.

Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>

diff --cc arch/arm/include/asm/unistd.h
Simple merge

diff --cc arch/arm/include/uapi/asm/unistd.h
Simple merge

diff --cc arch/arm/kernel/calls.S
Simple merge